Lecture (1) mycology, Dr



Lecture (1) mycology, Dr. kareema Amine Alkhafaji, Assistant professor.

Definition: mycology is the study of fungi .

General Characteristics of True Fungi (Mycota or Eumycota)

1. All are eukaryotic, fungi have a nucleus that surrounds and protects its DNA. Unlike animal cells, fungi have a rigid cell wall that is made of chitin. The fungal cell wall provides protection and support for the cell.   Inside the fungal cell wall is the cell or plasma membrane, which regulates the flow of substances into and out of the fungal cell. Fungi also have the following internal structures: nucleus, nucleolus, ribosomes (60S/40S), smooth and rough ER, Golgi apparatus, mitochondria, and a cytoskeleton.

2. Fungi exist in both large (macroscopic) and small (microscopic) forms. Macroscopic fungi include mushrooms and puffballs. One of the largest fungi ever found was 3.5 miles long and covered 2200 acres in Oregon. Another large fungi, discovered in Washington, covered 1500 acres and weighed 100 tons!

Microscopic fungi are dimorphic, which means that they exist in either of the two forms: multicellular mold or unicellular yeast.

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Most of fungi are filamentous Composed of individual microscopic long, hair-like filaments called hyphae(Mold), which exhibit apical growth and which branch to form a network of a visible mass of hyphae called a mycelium. Hyphae are used for absorbing nutrients and for sexual reproduction! 

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Unlike yeast, molds grow primarily OUTSIDE the human body and prefer temperatures below 30°C and can be found growing both at room temperature and inside the refrigerator. Molds also prefer acidic environments, which is why they can often be found growing on citrus fruit, cheese, and bread. Molds can reproduce either asexually or sexually using reproductive spores. During asexual reproduction, the bread mold (Rhizopus) releases spores that germinate (grow) to produce vegetative (feeding) hyphae. During sexual reproduction, the reproductive hyphae "mate" and produce a zygospore.

[pic][pic]bud scar

3. Some are unicellular e.g. yeasts. Yeasts are small, round, and unicellular.   Yeast reproduce asexually by a process called budding. During budding, the cell's genetic information is duplicated, creating an identical copy or clone of the original cell.   As

the new cell pinches off or buds from the surface, a bud scar is produced. [pic] 

Yeast prefer temperatures of 35-40°C and can grow INSIDE the human body. An example of this is the yeast, Candida albicans, which grows on the mucosal membranes of humans and other animals. Yeast also play an important role in the food industry, where they are used bread- and cheese-making , as well as in beer and wine production . This type of yeast is called Brewer's yeast (Saccharomyces cerevisiae). 4. Protoplasm of a hypha or cell is surrounded by a rigid wall Composed primarily of chitin and glucans, although the walls of some species contain cellulose.

5. Many reproduce both sexually and asexually. Both sexual and asexual reproduction often result in the production of spores.

6. Their nuclei are typically haploid and hyphal compartments are often multinucleate Although the Oomycota and some yeasts possess diploid nuclei.

7. All are achlorophyllous. They lack chlorophyll pigments and are incapable of photosynthesis.

8. All are chemoheterotrophic (chemo-organotrophic)They utilise pre-existing organic sources of carbon in their environment and the energy from chemical reactions to synthesize the organic compounds they require for growth and energy.

9. Possess characteristic range of storage compounds e.g. trehalose, glycogen, sugar alcohols and lipids.

10. May be free-living or may form intimate relationships with other organisms i.e. may be free-living, parasitic or mutualistic (symbiotic).

Hyphal Ultrastructure

Diagram illustrating the ultra structure of a septate hypha [pic]

• Each HYPHA is: essentially a tube - consisting of a rigid wall and containing protoplasm .tapered at its tip - this is the region of active growth (i.e. the extension zone). SEPTA (cross-walls), if present, can usually be observed down a light microscope .some fungi possess septa at regular intervals along the lengths of their hyphae in others, cross-walls form only to isolate old or damaged regions of a hypha or to isolate reproductive structures. some septa possess one of more PORES - such septa divide up the hyphae into a series of interconnected HYPHAL COMPARTMENTS, rather than separate, discrete cells. The PLASMA MEMBRANE is closely associated with the hyphal wall and in some regions may even be firmly attached to it - making it difficult to plasmolyse hyphae.Each hyphal cell or compartment normally contains one or more NUCLEI. In species whose septa possess a large central pore, the number of nuclei within a hyphal compartment won't remain static because the septal pore. Other nuclei are able to pass between adjacent compartments, via the central CYTOPLASMIC ORGANELLES are those commonly found in all eukaryotic cells.

The benefit and disadvantages of fungi

Abundant worldwide, most fungi are inconspicuous because of the small size of their structures, and their cryptic lifestyles in soil, on dead matter, and as symbionts of plants, animals, or other fungi. They may become noticeable when fruiting, either as mushrooms or molds. Fungi perform an essential role in the decomposition of organic matter and have fundamental roles in nutrient cycling and exchange. They have long been used as a direct source of food, such as mushrooms and truffles, as a leavening agent for bread, and in fermentation of various food products, such as viniger,wine, beer, and soy sauceFungi are also grown in large vats to produce flavorings for cooking, vitamins and enzymes for removing stains. Since the 1940s, fungi have been used for the production of antibiotics In addition to their role in food production, Fungi also play an important role in the production of natural antibiotics. The first natural antibiotic (penicillin) discovered was produced by the fungus, Penicillium, Drugs made from fungi cure diseases and stop the rejection of transplanted hearts and other organs.and, more recently, various enzymes produced by fungi are used industrially and in detergents Some species of yeasts and mycelial fungi are used in processes aimed at reducing the concentrations and toxicities of waste materials, particularly from industrial processes, before those wastes are released into the environment - a process known as bioremediation.. Fungi are also used as biological pesticides to control weeds, plant diseases and insect pests.

* Many species produce bioactive compounds called mycotoxins, such as alkaloids and polyketides, that are toxic and carcinogenic to animals and humans. *The fruiting structures of a few species contain psychotropic compounds and are consumed recreationally or in traditional spiritual ceremonies.* Fungi can break down manufactured materials and buildings, and* become significant pathogens of humans and other animals. *Losses of crops due to fungal diseases (e.g. rice blast disease) or food spoilage can have a large impact on human food supplies and local economies.

FUNGAL PATHOGENICITY

The ability of fungi to cause disease appears to be an accidental phenomenon. With the exception of a few dermatophytes, pathogenicity among the fungi is not necessary for the maintenance or dissemination of the species.

The two major physiologic barriers to fungal growth within the human body are temperature and redox potential. Most fungi are mesophilic and can not grow at 37 °C. Similarly, most fungi are saprophytic and their enzymatic pathways function more efficiently at the redox potential of non-living substrates than at the relatively more reduced state of living metabolizing tissue. In addition, the body has a highly efficient set of cellular defenses to combat fungal proliferation. Thus, the basic mechanism of fungal pathogenicity is its ability to adapt to the tissue environment and to withstand the lytic activity of the host's cellular defenses. In general, the development of human mycoses (fungal infections) is related primarily to the immunological status of the host and environmental exposure, rather than to the infecting organism. A small number of fungi have the ability to cause infections in normal healthy humans by (1) having a unique enzymatic capacity, (2) exhibiting thermal dimorphism and (3) by having an ability to block the cell-mediated immune defenses of the host. There are then many opportunistic" fungi which cause infections almost exclusively in debilitated patients whose normal defence mechanisms are impaired. The organisms involved are cosmopolitan fungi which have a very low inherent virulence. Currently, there has been a dramatic increase in fungal infections of this type, in particular candidiasis, cryptococcosis, aspergillosis, and zygomycosis. More recently described mycoses of this category include hyalohyphomycosis and phaeohyphomycosis. Altogether, some 200 "human pathogens" have been recognized from among an estimated 1.5 million species of fungi.

Classification of FUNGAL INFECTIONS

Superficial Mycoses includes:

Dermatophytes infection

Candidal infection

Malassesial infection

Piadra

Subcutaneous Mycoses

Systemic mycosis

Opportunistic Systemic Mycoses

Fungi harm the human by one of the followings:

• Hypersensitivity - an allergic reaction to molds and spores

• Mycotoxicoses - poisoning of man and animals by food products contaminated by fungi which produce toxins from the grain substrate

• Mycetismus - the ingestion of toxin (mushroom poisoning)

• Infection - tissue invasion with a host response

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SKIN MYCOLOGY

The Superficial Mycoses :These are superficial cosmetic fungal infections of the skin or hair shaft. No living tissue is invaded and there is no cellular response from the host. Essentially no pathological changes are elicited. These infections are often so innocuous that patients are often unaware of their condition.

Pityriasis versicolor A chronic, superficial fungal disease of the skin characterized by well-demarcated white, pink, fawn, or brownish lesions, often coalescing, and covered with thin fine scales. The colour varies according to the normal pigmentation of the patient, exposure of the area to sunlight, and the severity of the disease. Lesions occur on the trunk, shoulders and arms, rarely on the neck and face, and fluoresce a pale orange colour under Wood's ultra-violet light. Young adults are affected most often, but the disease may occur in childhood and old age.

Distribution: World-wide but more common in tropical than temperate climates.

Etiological Agent: Malassezia furfur a lipophilic yeast forming part of the normal flora of human skin.

The Cutaneous Mycoses

These are superficial fungal infections of the skin, hair or nails. No living tissue is invaded, however a variety of pathological changes occur in the host because of the presence of the infectious agent and its metabolic products.

Dermatophytosis - Ringworm or Tinea

Ringworm of scalp, glabrous skin, and nails caused by a closely related group of fungi known as dermatophytes which have the ability to utilize keratin as a nutrient source, i.e. they have a unique enzymatic capacity called keratinase enzyme.

The disease process in dermatophytosis is unique for two reasons:

(a) No living tissue is invaded the keratinized stratum corneum is simply colonized. However, the presence of the fungus and its metabolic products usually induces an allergic and inflammatory eczematous response in the host. The type and severity of the host response is often related to the species and strain of dermatophyte causing the infection.

(b) The dermatophytes are the only fungi that have evolved a dependency on human or animal infection for the survival and dissemination of their species.

Dermatophytes consists of three genera; epidermaphyon, trichophyton and microsporom. And can be divided into 3 broad epidemiological groups.

GEOPHILIC These dermatophytes normally inhabit the soil where they are believed to decompose keratinaceous debris. Some species may cause infections in animals and man following contact with soil (e.g. Microsporum gypseum).

ZOOPHILIC These dermatophytes are primarily parasitic on animals. Infections may be transmitted to man following contact with animal host (e.g. Microsporum canis).

ANTHROPOPHILIC These dermatophytes are primarily parasitic on man and have only rarely been known to infect animals, presumably following contact with man (e.g.Trichophyton rubrum).

The Subcutaneous Mycoses

These are chronic, localized infections of the skin and subcutaneous tissue following the traumatic implantation of the aetiologic agent. The causative fungi are all soil saprophytes of regional epidemiology whose ability to adapt to the tissue environment and elicit disease is extremely variable.

Sporotrichosis

Primarily a chronic mycotic infection of the cutaneous or subcutaneous tissues and adjacent lymphatics characterized by nodular lesions which may suppurate and ulcerate. Infections are caused by the traumatic implantation of the fungus into the skin, or very rarely, by inhalation into the lungs. Secondary spread to articular surfaces, bone and muscle is not infrequent, and the infection may also occasionally involve the central nervous system, lungs or genitourinary tract.

Distribution: World-wide particularly tropical and temperate regions.

Aetiological Agent: Sporothrix schenckii, commonly found in soil and on decaying

vegetation.

Chromoblastomycosis

A mycotic infection of the cutaneous and subcutaneous tissues characterized by the development in tissue of dematiaceous (brown-pigmented), planate-dividing, rounded sclerotic bodies. Infections are caused by the traumatic implantation of fungal elements into the skin and are chronic, slowly progressive and localized. Tissue proliferation usually occurs around the area of inoculation producing crusted, verrucose, wart-like lesions.

Distribution: World-wide but more common in bare footed populations living in

tropical regions .

Aetiological Agents: Various dematiaceous hyphomycetes associated with decaying

vegetation or soil, especially Phialophora verrucosa, Fonsecaea

pedrosoi, F. compacta and Cladosporium carrionii.

Mycetoma

A mycotic infection of humans and animals caused by a number of different fungi and actinomycetes characterized by draining sinuses, granules and tumefaction. The disease results from the traumatic implantation of the aetiologic agent and usually involves the cutaneous and subcutaneous tissue, fascia and bone of the foot or hand. Sinuses discharge serosanguinous fluid containing the granules which vary in size, colour and degree of hardness, depending on the aetiologic species, and are the hallmark of mycetoma.

Distribution: World-wide but most common in bare-footed populations living in

tropical or subtropical regions.

Aetiological Agents: Actinomycotic mycetoma: Nocardia, Actinomadura and

Streptomyces. Eumycotic mycetoma: Madurella, Acremonium, Pseudallescheria,

Exophiala, Leptosphaeria, Curvularia, Fusarium, Aspergillus etc

Clinical Techniques in Mycology A.    Visualization of fungi in tissue preparations 1.Treatment with 10% potassium hydroxide 2. Positive stain with a. Lactophenol cotton blue b. Grocott silver stain c. Hematoxylin d. Eosin 3. Negative stain with India ink B.Fluorescence of fungi under ultraviolet light by using Wood's light examination C.Culture of fungi on 1. Sabouraud's agar (favors fungal growth because of low pH) 2. Mycosel agar (selective for pathogenic fungi because of chloramphenicol and cycloheximide in medium)

D.Visualization of cultured fungi (25oC and 37oC)

1.Colonial morphology 2.Cellular morphology

a.    Hyphal morphology

(1)    Aseptate or coenocytic fungi (lack of septa) (2)Septate

(a)Regular connection (b)Clamp connection b.Spore morphology

(1) Conidiospore (2) Sporangiospore (3) Arthrospore (4) Chlamydospore c.Yeast morphology

(1) Size (2)Thickness of walls (3)Capsule presence/absence

E.Identification of yeast by

1.    Biochemical tests 2.    Behavior in broth and serum (germ tube formation) 3.ehavior on cornmeal agar (pseudohyphae formation)

زادك في سطور

الإمام علي (ع ) : الإيثار أعلى المكارم . عن الإمام الـصـادق (ع ) : يـعـيـش الـنـاس بإحسانهم أكثر مما يعيشون بأعمارهم , ويموتون بذنوبهم أكثر مما يموتون بآجالهم.

عن الإمام عـلـي (ع ) : إن الدنيا منقطعة عنك , والآخرة قريبة منك عـنه (ع ) : اجعلوا اجتهادكم فيها التزود من يومها القصير ليوم الآخرة الطويل , فإنها دار عمل ,والآخرة دار القرار والجزاء.

عنه (ع ) : كيف يعمل للآخرة المشغول بالدنيا؟ عن رسـول اللّه (ص ) : إن الـمـؤمـن لـيـسـكـن إلى المؤمن كما يسكن قلب الظمآن إلى الماء البارد.

عـنـه (ص ) : إذا رأيتم أهل الريب والبدع من بعدي فاظهروا البراءة منهم , وأكثروا من سـبـهم ,والقول فيهم والوقيعة , وناهبوهم كي لا يطمعوافي الفساد في الإسلام , وتحذرهم الناس ولا يتعلموا مـن بـدعـهـم , يـكـتـب اللّه لـكـم بـذلـك الـحسنات , وترفع لكم بها الدرجات في الآخرة. عن رسول اللّه (ص ) : أما علامة البار فعشرة :يحب في اللّه , ويبغض في اللّه , ويصاحب في اللّه ,ويـفـارق في اللّه , ويغضب في اللّه , ويرضى في اللّه ,ويعمل للّه , ويطلب إليه , ويخشع للّه خائفا مخوفا طاهرا مخلصا مستحييا مراقبا, ويحسن في اللّه. عـنـه (ع ) : عـجبت للبخيل يستعجل الفقر الذي منه هرب , ويفوته الغنى الذي إياه طلب ,فيعيش في الدنيا عيش الفقراء , ويحاسب في الآخرة حساب الأغنياء. عن رسـول اللّه (ص ): ثـلاث مـن أبواب الـبـر : سخاء النفس , وطيب الكلام , والصبر على الأذى.

عن رسـول اللّه (ص ) : مـن خـرج من ذل المعصية إلى عز الطاعة آنسه اللّه عزوجل بغير أنيس ,وأعانه بغير مال.

عن الإمام زيـن الـعـابـدين (ع ) : علامات المؤمن خمس : الورع في الخلوة , والصدقة في القلة ,والصبر عند المصيبة , والحلم عنـد الغضـب ,والصدق عند الخوف.

عنه (ص ) : المؤمن من آمنه الناس على أنفسهم وأموالهم.

عن رسول اللّه (ص ) : صنفان من أهل النار لم ارهما: قوم معهم سياط كأذناب البقر يضربون بـهـاالـناس , ونساء كاسيات عاريات , مميلات مائلات , رؤوسهن كاسنمة البخت المائلة ,لايدخلن الجنة ولا يجدن ريحها , وان ريحها ليوجد من مسيرة كذا وكذا.

عن الإمام الـباقر (ع ) : سئل رسول اللّه (ص ) : أي الأعمال أحب إلى اللّه عزوجل ؟ قال : إتباع سرور المسلم , قيل : يا رسول اللّه , وما إتباع سرور المسلم ؟ قال : شبع جوعته , وتنفيس كربته ,وقضاء دينه.

عن الإمام الصادق (ع ) : من أحب الأعمال إلى اللّه تعالى زيارة قبر الحسين (ع ).

عن رسول اللّه (ص ) : اشد الناس عذابا يوم القيامة عالم لم ينفعه علمه

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